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Active Site Local Environment Allows Acidic and Basic Synergy in Enzymatic Ester Hydrolysis by PETase
Summary
Atomic-level analysis of PETase enzyme kinetics revealed that high buffer pH improves nucleophilic attack on PET ester bonds while local hydrogen bonding stabilizes the hydrolysis transition state, suggesting two engineering strategies to enhance enzymatic PET degradation. This mechanistic insight directly advances microplastic pollution research by identifying molecular targets for engineering more effective plastic-degrading enzymes capable of breaking down PET microplastics in environmental and industrial settings.
Abstract Polyethylene terephthalate (PET) is a commonly used plastic worldwide and reducing its prevalence is crucial to improving environmental pollution. PETase that degrades PET plastic have received a lot of attention recently. This paper evaluates the ester hydrolysis process under both acidic and basic conditions, and shows that the local environment of the protein active site takes advantage of both. High pH in the protein buffer creates a better nucleophile to attack the ester through a proton shuttle channel in the protein, while local hydrogen bonds to the carbonyl of the ester stabilizes the intermediate/transition state of the hydrolysis reaction. With the understanding at the atomic level, we propose two engineering directions that can potentially improve the reactivity of the PETase: 1) increase the alkaline stability of the protein in general; 2) perturb the local hydrogen bond network to increase the partial charge on the PET carbonyl to be hydrolyzed. Abstract Figure